Background: Depression is common in patients with cancer and is associated with lower treatment adherence and reduced quality of life. Antidepressants and psychotherapy have limited success in improving depression among patients with cancer. This study explored the safety, feasibility, and efficacy of psilocybin-assisted therapy in patients with cancer and major depressive disorder.

Methods: This phase 2, open-label trial enrolled patients with curable and noncurable cancer and major depressive disorder at a single community oncology practice site. A single 25-mg dose of psilocybin was administered simultaneously to cohorts of three to four participants with individual (4.25 hours in 1:1 therapist-to-patient ratio) and group therapeutic support (3.75 hours) before, during, and after psilocybin administration. Outcomes included depression severity, anxiety, pain, demoralization, and disability.

Results: Thirty participants completed the study. No psilocybin-related serious adverse events occurred; treatment-related adverse events (e.g., nausea, headache) were generally mild and expected. There were no laboratory or electrocardiogram abnormalities. No suicidality was reported. Efficacy was suggested with a robust reduction in depression severity scores from baseline to posttreatment of 19.1 points (95% CI, 22.3 to -16.0; p < .0001) by week 8. Eighty percent of participants demonstrated a sustained response to psilocybin treatment; 50% showed full remission of depressive symptoms at week 1, which was sustained for 8 weeks.

Conclusions: Psilocybin-assisted therapy in group cohort administration was safe and feasible in patients with cancer and depression. Efficacy was suggested based on clinically meaningful reductions in depressive symptoms. The novel, group-oriented format, compact delivery time, community cancer center setting, and one-to-one therapist-to-patient ratio could also add to therapeutic gains and efficiency of administration.

Trial registration: NCT04593563.

Plain language summary: Depression is common in patients with cancer and associated with lower treatment adherence, reduced quality of life, and limited response to antidepressants and psychotherapy. We conducted a phase 2 trial to study a single dose of psilocybin administered in a group therapy setting with one-to-one therapist-to-participant psychological support to patients with curable and noncurable cancer and major depressive disorder. Findings of the study showed safety (no treatment-related serious adverse events or suicidality) with psilocybin and suggested efficacy, with a significant reduction in depression severity scores from baseline to posttreatment. Further investigation is warranted.